Cell division

Question 1

where does DNA exist?

Answer 1

in the nucleus as thin strands

Question 2

what happens when the cells containing nuclei are ready to divide?

Answer 2

the DNA copies itself then coils and condenses to form chromosomes.

Question 3

what is each chromosome made up of?
what does each section of a single molecule of dna have?

Answer 3

a single molecule of DNA
-it contains a code for the production of a particular protein called a gene.

Question 4

what does each human body cell contain?
how could they be arranged?
what does each chromosome in this pair carry?

Answer 4

-46 chromosomes.
-into 23 pairs.
-the same types of genes.

Question 5

what is the 23rd pair?
difference between the female and male chromosomes + features?

Answer 5

-the sex chromosome
-females = XX (2 chromosomes that are identical in shape)
-males = XY (one of the chromosomes is different)

Question 6

cells divide when: (3)

Answer 6

-an organism grows
-an organism becomes damaged and needs to produce new cells for repair
-organisms like bacteria reproduce asexually

Question 7

what is essential for the new cells produced to contain?

Answer 7

genetic information that is identical to the parent cell.

Question 8

describe the stages of a cell cycle: (5)

Answer 8

• cell cycle involve cell growth, synthesis of DNA.
• chromosome produces an exact copy of itself.
  -after this a period of further growth occurs and the DNA is checked for errors.
  -mitosis occurs after this checking has been completed.
  -finally the cytoplasm of the cell separates and two cells are formed.

Question 9

what happens during mitosis?
what is produced?

Answer 9

-diploid cell undergoes a type of cell division
-two genetically identical diploid daughter cells

Question 10

the length of different stages of the cell cycle can be estimated using the formula:

Answer 10

length of time in phase = (observed number of cells at that stage/ total number of cells observed) x total length of time of cell cycle

Question 11

what are the daughter cells? and why?

Answer 11

clones of each other
-as every base pair of their DNA is identical.

Question 12

interphase: (2)

Answer 12

-the cell spends most of its life in this phase.
-the DNA in chromosomes copies itself ready for mitosis

Question 13

prophase: (2)

Answer 13

-the DNA in chromosomes and their copies condenses to become more visible.
-the membrane around the nucleus disappears.

Question 14

metaphase:

Answer 14

Chromosomes and their copies line up in the middle of the cell.

Question 15

anaphase:

Answer 15

Chromosomes and their copies are pulled to different ends of the cell.

Question 16

telophase:

Answer 16

New membranes form around the chromosomes at each end of the cell.

Question 17

cytokenesis:

Answer 17

The cell membrane pinches in and eventually divides into two daughter cells.

Question 18

what happens when a cell becomes cancerous? (2)

Answer 18

-it begins to grow and divide uncontrollably.
-new cells are produced even if the body does not need them

Question 19

what does a group of cancerous cells produce?

Answer 19

a growth called a tumour.

Question 20

what are the two types of tumours?

Answer 20

benign and malignant

Question 21

characteristics of a benign tumour: (3)

Answer 21

-grow slowly.
-usually grow within a membrane, so can easily be removed
-do not invade other parts of the body.

Question 22

characteristics of a malignant tumour? (3)

Answer 22

-grow quickly.
-invades neighbouring tissues and can spread to other parts of the body in the bloodstream.
-as the tumour grows, cancer cells detach and can form secondary tumours in other parts of the body.

Question 23

what is the process of cancer cells detaching and forming secondary tumours in other parts of the body called?

Answer 23

metastasis

Question 24

what are cancer cells? (in terms of functionality)
-what does this mean?

Answer 24

undifferentiated – they do not carry out their normal function.

Question 25

how do genetics play a part in cancer?

Answer 25

genetic factors that increase the likelihood of developing some cancers

Question 26

what are carcinogens?

Answer 26

Chemicals and other agents that can cause cancer

Question 27

what do carcinogens do? and how? (2)

Answer 27

-cause cancer by damaging DNA.
-as they cause mutations to occur

Question 28

why are we more likely to develop cancer as we get older? (3)

Answer 28

-a single mutation will not cause cancer.
-several are required for this to occur.
-hence we are more likely to develop cancer as we get older.